The Slender Chronicles
by Moriabbey
Summary: After months of strange behavior, Isabella disappears in Danville Forest one night. The rest of the gang is determined to find out what happened to her, but when they begin to search, they uncover secrets more terrible than anything they'd ever imagined. Rated T for creepiness in the prologue and later on.
1. Prologue

**Isabella's POV**

Isabella stumbled through the darkened woods, flashlight shaky in her trembling grip. Its light flitted between the trees like a frightened butterfly. Somewhere in the trees behind her, there was the sound of a cracking twig. She let out a gasp and whirled around, a look of terror on her face. She ran her flashlight around the trees for a moment, before deciding there wasn't anything there. She turned back around and started stumbling through the forest again.

Occasionally, she would turn around and look over her shoulder, like there was something chasing her. Her breath came in short, panicked gasps. Her clothes were ripped and torn, and the satchel slung over her shoulder looked like it was held together with spit and prayers.

In the late-night darkness, and with Isabella's fragile state of mind, her environment seemed malevolent, even hostile. Their branches seemed like tentacles, reaching out to seize her and pull her in. Whenever she ran into a branch, she would gasp in panic, and then realize it was just a branch and keep running.

Of course, given the circumstances, her reaction could hardly be criticized.

She stumbled over a root and landed on her face. The flashlight flew out of her hand and landed in the dirt. The light clicked off. Isabella moaned and rubbed her arm where it had hit another root, and then realized what had happened. She started scrabbling madly through the dirt for her flashlight.

Behind her, a slim figure began to walk closer. Isabella didn't notice him; she was blind without the flashlight, and the figure was all but silent.

Suddenly, her fingers made contact with the cold metal of the flashlight. She breathed a sigh of relief as she picked it up and clicked the "on" button.

Nothing happened.

Her face fell. She clicked the button again, and then three times more in quick succession. It didn't turn on.

The slim figure grew closer.

She took no notice, madly trying to get the flashlight to turn on. When it finally did so, relief returned to her face. Then, barely a moment later, a feeling of dread began to overcome her. She gradually became cognizant of the figure standing behind her.

Ever so slowly, she turned her head over her shoulder. Her face, before a mask of relief, now slowly turned to terror.

"No..." she whispered. "Please, no..."

Her flashlight clicked off.

There was a scream.

And then there was silence.


	2. Chapter 1: Where's Izzy?

**Phineas' POV**

**Twelve hours later**

News vans and police cars crowded the Garcia-Shapiro house, spilling out from the driveway and onto the street. A small force of police officers manned the line of police tape around it, keeping out any overeager reporters, of which there seemed to be many. They mobbed the perimeter of the house, shouting questions that no one seemed interested in answering.

Inside the house, more police officers searched for evidence, photographing everything in sight and sticking anything that looked significant in an evidence bag. Vivian sat crying on a tattered couch, with Linda trying to comfort her. A police officer stood with them, apparently trying to assure them that they were making every effort to find Isabella.

"My little Izzy," Vivian sobbed. "What has happened to her?"

In the next room over, another police officer collected statements from the kids. Many of them seemed to be in shock: Phineas' characteristic smile was gone, Buford wasn't bothering Baljeet at all, and Ferb was talking even less than usual.

Isabella was conspicuously absent.

As Phineas wound up his statement, the officer made few final notes, and then nodded to Phineas.

"Alright, we're done here," he said. "You're all free to go." Then he got up to talk to another officer, leaving Phineas staring like he'd been hit over the head with a blunt object. All the other kids wore similar expressions.

"What's happened to her?" Phineas asked, his voice cracking a little bit.

No one needed to ask who he was talking about. Buford, in a rare show of compassion, reached out and put a hand on Phineas' shoulder.

"Don't worry, Dinner Bell," he said, managing to both use his pejorative nickname for Phineas and sound comforting in the same sentence. "They'll find her."

"The Danville Police Department is renowned across the Tri-State Area," Baljeet added. "If Isabella can be found, they will find her."

"I know..." Phineas said, his voice trailing off. "It's just... I feel like there's something wrong here. Something the police are missing."

"Phineas, these are professional crime solvers," Baljeet said. "What on earth could they be missing that we might notice?"

"I don't know... It's just a feeling. It's probably just what comes with having one of your best friends disappear in the middle of the night."

Baljeet reached out and put his hand over Buford's on Phineas' shoulder. "Well, you just went over the events with the police. Did you leave anything out in your testimony?"

Phineas looked up and glared at Baljeet.

"Do you really think I would do something like that?" he asked angrily. "I told them everything I knew. I just have a feeling there's something we're not noticing."

"Well, then, let us go over it again. We will see if there is anything any of us missed."

Phineas gave a tired sigh.

"Alright," he said, "Where do you want to start?"

After a moment of consideration, Baljeet decided "Well, you said she had been behaving strangely for a while now. When did you first notice that?"

Phineas gave a tired sigh and rubbed his temples. He took a few seconds to compose himself before speaking.

"It started about two months ago..." he began.

* * *

Who knows what happened? ME!

Well, kind of... Sort of... And I guess you all probably guessed it by now, anyways. It's kind of obvious, I suppose.

Anyways! Reviews:

**Sleeping Kangaroo: **Thanks, cuz! I feel like it was a bit short, honestly.

**Green-Finch 24601: **Yes. Yes, I have. And neither can I!

**Nehamee: **Excellent! That's exactly the impression I was going for!

**TheNargana: **Thanks. A lot of people seem to have got that impression, which I, for one, think is excellent.

**TheCartoonFanatic01: **I'll try. I can't wait to write this, either. But you'll get nothing out of me!

And, an announcement to any of you who are reading my other fic, Across the First Dimension: Sorry, but it's probably going to be a while until I can update. I haven't been making a lot of progress on the latest chapter. I'm really sorry, I'm going to try to finish it as soon as I can.

In the meantime, please R&R, everybody!


	3. Chapter 2: Phineas's Story

I forgot to mention this in my last chapter, but I am _very_ slow at updating. So, I'm sorry for taking so long with this chapter.

Also, a disclaimer: I do not own Phineas and Ferb, any of its characters, or the Slender Man.

Actually, I wonder if I could get a trademark on him...

* * *

**Phineas's POV**

**Two months ago**

Isabella stepped into the Flynn-Fletcher backyard and yawned.

"Sorry I'm late, guys," she said sleepily. "I'm a little tired. I didn't get a lot of sleep last night."

Phineas looked up from the device he and Ferb were tinkering with. "Oh, it's alright, Isabella," he said. "Could you bring me that socket wrench over there?"

She picked up the piece of metal he was pointing at and brought it over. "So, what are we building today?" she asked.

"Well," Phineas grunted as he took the tool Isabella brought him and began to force a component into place. "In theory, it'll let us see the emotions of people in the area. That screen will change color based on the prevalent emotions- red for anger, blue for sadness, stuff like that."

"What do you mean 'in theory?'" Isabella asked quizzically. "Your inventions always work."

"That's the thing," Phineas replied. "We've gone over the plans at least a dozen times already, but it still doesn't work like it's supposed to. Whenever we turn it on, we just get this."

He flicked a switch on the device, and instead of turning a single color, the screen showed a series of color bars, like you'd get on an old analog TV tuned to a test pattern. After a few seconds, the colors jumped into a reverse image of themselves, then started to flicker back and forth.

"We still haven't worked out exactly what's wrong with it," he continued. "Ferb thinks it's a problem with the emotional capacitor, but I still say it's just something with the screen connection."

"Yeah," Isabella said absently, like what Phineas had just said had gone over her head. "Hey, can I talk to you about something?"

"Sure," Phineas said.

Isabella waited a few seconds, and then added "Alone."

"Well, we're sort of in the middle of something here... Give me a few minutes."  
"Please, Phineas. It's really important."

Phineas looked up from the device at Isabella.

"Oh," he whispered when he saw her expression. "I... Yeah. Sure."

Ferb looked up from the other side of the device.

"I have to go for a second," Phineas said. "You can handle this without me, right?"

Ferb shot Phineas a look that seemed to say "Why do you even need to ask?"

Isabella led Phineas back into the house, shooting nervous glances over her shoulder all the way. Once they were inside, she gingerly closed the door behind them and started wringing her hands nervously.

"So, what's going on, Isabella?" Phineas asked. She opened her mouth, as if to speak, and then closed it again.

"I..." she started, but with her voice trailing off as soon as she started. When she tried again, the same thing happened a second time. She sighed.

"I don't know how to explain it," she said in a tired tone. "I don't even know where to start."

"Well, start at the beginning, then," Phineas said, trying for a bit of humor. Isabella didn't really react; she just slumped against the wall.

"Isabella?" Phineas asked. His voice was beginning to show a bit of concern. "Are you alright?"

She was silent for a moment before replying "I don't know, Phineas. I... I'm not really sure about anything anymore. I think I'm starting to see things when there isn't anything there, but I can never remember what I've seen. I'll sometimes wake up and realize that pieces of my memory are missing. And then..."

Her voice trailed off again. She looked around them again, and then leaned in closer to Phineas. "I sometimes feel like there's someone watching me. I'll look up and look around, but I never see anyone. I don't know what's going on... Oh, Phineas, please help me!"

She started crying. In spite of being caught flat-footed by the situation, it never crossed Phineas' mind to do anything besides comfort his friend. He stepped forward and wrapped his arms around Isabella. She didn't respond, except by doing the same.

Phineas didn't say a word; he just held her close as her tears ran down her cheeks. After about a minute, once her crying started to abate a little bit, he pulled away from her just enough to look into her eyes.

"It's going to be okay, Isabella," he whispered soothingly. "Have you told anyone else?"

She shook her head, her eyes still filled with tears. "No, you're the first. I was afraid anyone else I told would think I was going crazy." She sniffed, and asked "You don't think I'm crazy, do you?"

Phineas shook his head. Isabella fell back into his arms, crying again.

There was a knocking at the back door. Phineas looked over Isabella's shoulder and saw Ferb through the window set into the door.

"Not now," he mouthed, and motioned for Ferb to leave them alone. Isabella looked back to see what was going on.

"It's fine," she said, and added, with a weak smile "I can handle myself for a few minutes." Phineas looked at her with an expression of concern.

"You sure?" he asked. She nodded.

With apparent reluctance, Phineas walked over to Ferb and began to help him resolve some technical issue with the device. Isabella stood where she was, still sobbing a little bit, but making an apparent effort not to cry in front of Ferb.

Suddenly, something in a window caught her eye. She turned to see what it was.

She let out an audible gasp.

Her scream filled the room.

Phineas turned at the terrible noise and ran to her side.

"Isabella?!" he exclaimed in a panicked tone. "What happened?"

She didn't answer; she just continued staring. Phineas followed her terrified gaze out the window.

He didn't see anything.

He nervously turned back to Isabella. "Um... Isabella?" he asked. "Do you see something?"

She stammered something incoherent, and then stopped, like she'd meant to say something else. She tried again, and once again only managed to stutter.

After taking a moment, apparently to compose herself, she said "I... I have to go."

"You- what?" Phineas asked, now just sounding confused. "What do you mean?"

"I mean I have to go."

"What? Why?"

"... There's something I forgot about. Homework."

"It's summer vacation!"

Isabella ignored Phineas' protestations and ran across the room to the front door. She opened it, ran through, and shut it behind herself with a slam.

**Phineas's POV**

**Present day**

"And that was it?" Baljeet asked astonishedly.

Phineas nodded. "I went over to her house afterwards, but nobody came to the door. She came back over the next day, but when I asked her about what happened, she just clammed up about it. I left it alone after that."

"Wow..." Baljeet whispered. "She always seemed fine whenever I talked to her. I can hardly believe it."

"I know," Phineas said. "I'd never seen her like that before. She'd always been the one of us who kept her head under pressure, but she seemed so scared. She made me scared for her, too."

He sighed. "And I can't help feeling like this is my fault..."

Before anyone else could respond to that, one of the policemen (and women) milling about in the Garcia-Shapiro household came up to them and asked "Are you Isabella's friends?"

Ferb nodded.

"Well, you'd better come with me," the policeman continued. "We've found something you'll want to see." None of the children argued with him; they were all eager to know just what had been found.

He led them into one of the rooms at the back of the house, where a higher-rank looking police officer was waiting. A few moments after the kids had arrived, Mrs. Garcia-Shapiro and the Flynn-Fletcher parents came in as well.

"Have you found my Isa?" Vivian asked through sobs. The police officer shook his head. Vivian very nearly burst back into tears.

"We've managed to track Isabella's footprints through Danville Forest," the officer began. "They start on one of the trails, but soon go far into the forest itself, before ending far from just about everywhere." He pulled a plastic evidence bag from behind his back. "This was all we found."

Inside it was a long black flashlight. On the end cap, ground jaggedly into the metal, was a circle with an "X" through it. Under it was carved was a single word:

"Watching."

* * *

Thanks to everyone who reviewed:

**woodland5 (anonymous):** Everyone else seems to be doing that, actually.

**Sleeping Kangaroo: **Honestly, I prefer long and sweet

**Yarthayaj'knaushtavdhladleklwa: **Not gonna say. My lips are sealed /zips up mouth/

**AuthorD: **I hope so.

**TheCartoonFanatic01: **... Well, this isn't quite ASAP, but I'm hoping you'll be willing to read it anyways.

**OC RADIO FM 365: **Can't wait to write more!


	4. Chapter 3: Vector Algebra (or is it?)

**Phineas**

The officer passed around the evidence bag for everyone to examine, but unsurprisingly, no one seemed particularly eager to look at it. Only Baljeet took it and said, with an astonished expression, "I know that symbol!"

"You do?" Phineas asked in astonishment. Baljeet nodded.

"I do," he replied. "It is unmistakable."

"Well, don't leave it at that, son," the police officer said. "Anything you can tell us might help us find her."

Baljeet looked up from the evidence bag and exclaimed "The circled 'X' is the symbol for the tensor product of two vectors! She must have been studying advanced vector algebra!"

Everyone else in the room let out a groan of frustration simultaneously. "What?" Baljeet asked in a confused tone.

"I vote we don't let him in to the next one of these briefings," Buford said. The police officer groaned again and facepalmed himself.

"Alright, so much for that line of reasoning," he muttered. "Does anybody have an actually good suggestion?"

There was no response. The police officer sighed.

"Well, I guess that's it, then. I just wanted to tell you all about the new evidence. If anyone comes up with anything, please tell us."

He walked out of the room, probably to go confer with the other police officers. Vivian broke down into tears again, and Linda lead her out, supporting her head on her shoulder. Lawrence followed his wife. The kids merely sat there, staring blankly into space.

Baljeet, recognizing Phineas' despondence, thought quickly and resumed his psychiatrist bit.

"So, how did Isabella act after that?" he asked.

"She was... She was actually really normal up until she disappeared," Phineas said. "She showed up the next day and pretended like nothing happened. Everyone was asking her about it, but she just acted like she didn't know what we were talking about."

"She did not exhibit any unusual behavior after that?"

"No. She seemed fine to me."

Baljeet patted Phineas on the arm and said "Let's all go for a walk. It will be good to get our minds off of all of this."

**Two months ago**

**Isabella**

Isabella walked through the door, tears streaming down her cheeks. "Isa," her mother called out. "What are you doing back so soon, my little flower?"

"Just leave me alone!" Isabella yelled back, barely able to keep the sobs out of her voice. She ran into her room and locked/slammed the door behind her, then sat against it, cradled her head in her hands, and let herself cry.

Behind the door, she could hear her mother knocking and asking what was wrong. She knew Vivian couldn't help her; she hadn't been safe even with Phineas, so why would her mother be able to do anything for her?

She left after a few minutes. Isabella didn't move from her position against the door. After a few more minutes, she finally managed to stop her sobbing enough to haul herself onto her bed.

When she looked up again, her eyes stained red, she saw something outside of her window; the same slender figure she'd seen at Phineas' house.

"What do you want from me?!" she cried, her voice nearly cracking from the strain. "Why can't you leave me alone?!"

She dropped her head into her arms, and when she looked up again, the figure was gone.

This failed to comfort her.

Vivian came back to the door and started knocking again, sounding more concerned this time. "Isabella?" she called out. "Who is in there with you? Are you alright, my little flower?"

Isabella lifted her face up long enough to scream "GO AWAY, MOTHER!" before dropping her face back down with a sob.

Vivian seemed to hesitate. "I..." she said. "Alright. If you want to talk, Isa, I'll be... I'll be out here."

Isabella heard her mother walk away, and curled herself into a fetal position.

_I'm all alone..._ she thought to herself.

* * *

Thanks to everyone who reviewed:

**Yarthayaj'knaushtavdhladleklwa:** As I've said before, I cannot comment on future events of the story.

**AuthorD: **I've actually been watching a lot of Slender Man ARGs for this fic. I've made it through Marble Hornets and I'm working through TribeTwelve and EverymanHYBRID.

**TheCartoonFanatic01:** Sorry. Can't say (not yet, anyways).

**EDD17SP: **Yeah. I've learned the same thing about Slender Man vids.

**Sleeping Kangaroo: **ALWAYS PHINBELLA

**Green-Finch24601:** I know. She's going to be taking quite a beating in both of my fics...

And I apologize for my terrible update schedule with both this fic and Across the First Dimension. Just please bear with me and I promise I will get new chapters up, if not in a terribly timely fashion, then eventually!


	5. Chapter 4: A bit of Rest

**Phineas**

The rain drizzled on the pavillion in the Danville Forest. After finding it at the end of the two-mile walk here, the kids had decided to take shelter in it. Everyone seemed a bit worn out from the walk, and still a bit shell-shocked from Isabella's disappearance. Taken together, the overall mood was one of tense uneasiness. All the kids wore glum expressions, especially Phineas and the Fireside Girls.

Baljeet, even though his idea to get everyone's minds off of things with a walk through the forest had failed thus far, was not ready to give up on it yet.

"You know, forests have always creeped me out," he said, and waited for a response. None were forthcoming.

"Not deciduous forests," he continued, not quite ready to give up yet. "Coniferous trees are the ones that creep me out- the ones with leaves. Especially in the winter, when all their leaves have fallen off. I keep imagining that their dead branches are arms, reaching out for me."

Phineas looked up from the pavillion. All the trees around were covered in either leaves or pine needles, and none of their branches looked much like arms.

"I don't see it," Phineas said.

Baljeet groaned and started looking around, apparently grasping for a new conversation topic.

"... How about that blackout we had?" he finally settled on.

Phineas looked up again. "The one from two months ago?"

Baljeet nodded. "You know, it was a very unusual blackout. It was too long to just be a transient fault, but probably too short to be a power failure- I clocked it at about a minute. And it only affected our block- it is very rare for power failures to be that specific."

"Yeah, I remember that blackout," Buford chipped in. "I remember Biff's night light went out, so I had to make a gas lamp with my breath. Of course, the lights came on right when I finished building it, so I had to find something else to use it for."

"So that was you!" Baljeet exclaimed. "I had thought someone dropped a tear gas canister in my window."

"Close enough," Buford said.

The kids were silent again.

"Hey, Phineas," Adyson piped up. "You remember how you said Isabella was acting normal after... Whatever it was that happened at your house?"

"Yeah."

"Well, that's... That's not the impression we- that is, the Fireside Girls- got."

Phineas turned to her with a confused expression.

"What do you mean?" he asked.

"It wasn't anything really obvious. Not, like, she tried to attack us or anything."

"Yeah..." Phineas said expectantly.

"But right up until she was taken, we could tell there was something wrong with her. She was... I dunno, withdrawn. She didn't talk to us as much as usual. She even started relegating most of her leadership decisions over to us- well, to me, mostly."

"Did you tell the police about this?" Phineas asked.

"Yeah. They told us not to worry about it. I think the phrase they used was 'teenage angst,' but it was more than that. Most of us had been with her for years, and we could tell there was something really, really wrong with her."

"Don't forget the nosebleeds!" Holly chimed in.

"Oh, right," Adyson continued. "She kept having nosebleeds all through our meetings."

"She- really?" Phineas asked. "I didn't see anything like that when she was at our house."

"... I think she said something about plugging up her nose with tissues whenever she was at your guys'."

Phineas was silent, and then looked down at the floor of the pavillion.

"Wow..." he whispered to himself.

Suddenly, a flash of yellow wedged between the floor and the wood sticking up from it caught his eye. He bent over to examine it, and found a piece of aged paper in the joint. He pulled it out.

Baljeet and Ferb, being at his sides, leaned over to look at the paper.

"Well, that is certainly... Interesting," Baljeet said. Ferb, in his usual manner, said nothing, but raised an eyebrow.

At first glance, it looked like a crude drawing of a forest, and not much of a forest at that; barely ten trees. The trees themselves were quite poorly drawn, like each of them had been scribbled into existence in less than a moment. But this striking lack of quality didn't take away from the drawing; if anything, it seemed to enhance it. It gave it an ominous air, one of fear and foreboding.

That's what a first glance showed. But a closer inspection revealed that one of the trees was out of place; in fact, it was not a tree at all. It was a stick figure, drawn with the same careless quality as the trees. If the drawing seemed ominous without the figure, it became almost terrifying with it; as far as a drawing could be.

Phineas stared at it for a moment, his eyes locked with an almost supernatural attraction.

Then Ferb's phone started to ring.

Ferb pulled out his phone and checked the caller id.

"Who is it?" Baljeet asked.

"It's Lawrence," Ferb replied, and put the phone to his ear.

The conversation was very short, consisting of a brief greeting from Ferb, about a minute of Lawrence speaking, and then a quick goodbye.

"Well?" Baljeet asked.

"He says we need to come home," Ferb said. "There's some government agents back at Isabella's house who want to ask us some questions."

"Government agents?" said Baljeet. "I thought we had already all given statements."

"Apparently not enough for the authorities," Ferb said. "Guess we'd better get back home."

Phineas seemed oblivious to all this. All through the phone call and even now, he'd just kept staring at the page.

Ferb, seeing his stepbrother apparently locked in place, put a hand on his shoulder and asked "Phineas?"

Phineas kept staring for a moment, then shook himself out of his daze.

"I... yeah. Sorry. Let's get back."

As the kids turned to follow Phineas and Ferb's lead, Phineas tossed away the page he clutched like a piece of scratch paper. As they began their short walk back to the house, a breeze caught the page and carried it up and away, just to the edge of the clearing the pavillion was in. And as the kids followed the trail to the edge of said clearing, the page began to fall, finally settling under one of the trees.

But this tree was not a tree. It was a figure as calm and implacable as them, a pale figure cloaked in formal attire and with a face as clear as fresh-fallen snow. He watched, silent as the trees, as the children walked away.

* * *

**thedoraemons7:** PHINBELLA FOREVER

**Yarthayaj'knaushtavdhladleklwa:** My lips are sealed like the gates of the Forbidden City!

**AuthorD:** I can't wait to _write _the next chapter!

**TheCartoonFanatic01: **Well, you'd be surprised about Isabella... But I'm not saying about the Rake!

**SleepingKangaroo:** Those are both exactly what I'm going for!

**gamelover41592:** I know.


	6. Chapter 5: New Mysteries

Before I start, I'd just like to make an announcement. I'm thinking of starting a Phineas and Ferb fanfiction set in the Dungeons and Dragons setting of Eberron, and I'd like to know how many people are familiar with the setting. There's a poll on my profile, and I would appreciate it if a few people would participate in it. Additionally, if anyone has any ideas for it, I'd love to hear them. I have a few already (mostly character concepts) but I'd love to hear anyone else's.

And for anyone who decides to talk part in the poll, I apologize in advance for the rough state of my profile page.

* * *

**Phineas**

Years of exposure to popular culture had taught the kids that large black vans without plates were suspicious. So, when they saw a pair of them sitting in their driveway, they knew that something was up.

Their suspicions were confirmed when they walked through the door and saw a pair of men with black sunglasses and suits talking to Vivian and Linda. Neither of them would have looked out of place in "Men in Black."

One of the men saw the kids coming in and tapped the other on the shoulder. He looked up from his interviewing and walked towards the children.

"Ah, Isabella's friends," he said. "We're from the Bureau. We'd like to ask you a few questions."

"The Bureau?" Baljeet asked. "What does the FBI want with a missing person case?"

"We're from a different Bureau," the other man replied. "We're from the Bureau of Special Investigations. It's our job to investigate cases like this."

He held out a thin business card with a phone number and "Bureau of Special Investigations" printed on it.

"I have never heard of such an agency."

"That means we're doing our job right."

"Is there somewhere private we could talk?" the first agent cut in. "We'd like to interview you individually if possible."

"There... There is Isa's room upstairs," Vivian said through sniffs and sobs. "But I think the police are still looking over it."

"That shouldn't be a problem," said the second agent. "We'll need to examine the room ourselves at some point anyway.

"Now, who wants to be interviewed first?"

Phineas quietly raised his hand. The second agent gave him a nod and said "Alright. The rest of you just wait down here until we're done."

Phineas followed the two agents upstairs to Isabella's room. One of them closed the door behind them as Phineas took a seat on the bed.

"So, what exactly did you want to know about?" he asked.

"We have a few standard questions we ask in cases like this," said the first agent.

"First, did she exhibit any unusual physical symptoms up to her disappearance."

... What? Phineas thought to himself. Out loud, he said "Um, I didn't see anything. Adyson said she had really frequent nosebleeds before she disappeared, though."

The first agent raised his eyebrows. The second one gave him a gentle smack, like he'd just violated some unspoken protocol.

"What about mental effects?" the first agent continued without acknowledging his partner. "Amnesia, paranoia, deja vu?"

"... What?" Phineas asked. These did not seem like regular police inquiries.

"Just answer the questions, please."

"She... Uh..." Phineas shook his head, apparently trying to clear his thoughts. "Well, like I said, I didn't see anything, but Adyson mentioned that she seemed withdrawn. You should really talk to her; I think she saw a lot more of Isabella than I did."

The two agents shared a strange look.

"Is there anything else?" the first agent asked after turning back to Phineas.

"No, I think that's it," Phineas said.

"Alright. We'll go get your brother, then. You can go wait with the rest of the kids."

The two men walked out of the room, and were just closing the door when Phineas realized that he had some questions of his own to ask them. Mostly just what was up with these weird questions.

"Hey, wait-" he said, and stood up from the bed to talk to them, but they'd already left the room.

He gave a sigh and sat back down. He was probably just still in shock and all those questions were standard in a missing person investigation.

Of course, he'd never heard of the "Bureau of Special Investigations." He made a note to ask Baljeet about it.

He looked up at the pictures plastered on the walls. Most of them were pictures of the group or their projects. He recognized the elevator to the moon, the time machine, the roller coaster...

Actually, a disproportionate number of the pictures were just of him. Mostly close-ups of his face.

Well, he supposed he was the dominant personality in most of their projects. Ferb did most of the actual work, but most people perceived him as the leader, so he supposed he would show up by himself in more of them.

That didn't explain the little hearts around some of the photos, though.

He would have to look into that later. Right now, one of the other photos caught his eye; a group shot of all of the kids from the time they built a giant bubble.

The background was filled with trees, which was understandable, seeing as they built the bubble machine in the Danville Forest. Everyone in the picture looked normal, but there was a spot of distortion behind Isabella, a blurry dark patch with a white bit on top of it. Over the whitish patch someone had scribbled, in red marker, the circled "x" symbol from Isabella's flashlight.

He heard the two agents coming back down the hallway. On an impulse, he stuck the picture in his pocket (even though he knew the room was technically a crime scene), then stepped out of Isabella's room.

Before he did, he stopped and placed a hand on Isabella's doorframe. "We miss you," he said quietly, and then slipped away down the stairs.

The rest of the kids were collected in a little group by themselves in the living room, all chatting idly about anything besides Isabella.

"Guys," he said as he sat down amongst them. "There's something you need to see."

He pulled out the photo and held it out to Baljeet, who took hold of it and began looking it over.

"This distortion is unusual," he said after a moment. "It is very localized. When a camera experiences interference, it usually results in the view just being very blurry, so that you cannot make out anything. This is... It is just an ovoid blob."

"So, what is it?" Phineas asked.

Baljeet was silent for another moment.

"... I'm not sure," he said finally. "This is really not my area of expertise. I could ask around; maybe do some internet research. I could get back to you in a few days."

Suddenly, Phineas looked around, as if looking for something.

"You know, I realize that he's been gone for most of the day," he said. "But where's Perry?" He groped around in his pocket as if looking for something. "And where's the card that agent gave me?"

Perry

The Flynn-Fletcher household was nearly empty, with both the parents and all three kids over at Vivian's house. Even so, Perry did a quick check of his surroundings before sucking himself down the tube behind behind the painting in the Flynn-Fletcher living room. He landed with a thump on his chair and turned on his lair monitor.

Major Monogram's face appeared on the screen.

"What? Agent P?" he asked. "I thought we gave you the day off after that business with Agent Pinky's sister."

He sighed.

"That poor girl. And Agent Pinky's in a right state about it. Just growls at anyone who gets close."

His gaze refocused, seeming to become more concentrated on the situation at hand.

"Anyways, what did you want, Agent P?"

Perry held up the business card from the agents that he'd swiped from Phineas. Monogram seemed to have to squint to read the fine lettering on the card.

"Bureau of Special Investigations?" he read off slowly. "I don't think I'm familiar with them. Are they a band?"

Perry pulled up some security footage from the Garcia-Shapiro household of the two agents. When it was finished playing, Monogram began to stroke his chin thoughtfully.

"This is most unusual," he said. "I don't remember sending any agents over to ask questions, and if I had, they probably wouldn't be humans. Carl!"

Carl slipped in from wherever he lurked just off the screen. "Yes?"

"I need you to research this 'Bureau of Special Investigations.' See what you can find out about them."

"I'll hit the internet right away, sir!"

Meanwhile, Perry slipped away. He had his own investigations to carry out.

* * *

Holy crap, I got ten reviews on this chapter. I think that's a personal record. Thanks, everyone, and special thanks to 14AmyChan and Ohfortheloveofpete for going back and reviewing the previous chapters too!

Thanks to all of you:

**Ohfortheloveofpete:** Yes. Yes, she is.

**Thedoraemons7: **Thanks! I hope so too.

**gamelover41592: **Well, according to quantum physics, particles that you have not yet observed the state of exist in a superposition of all possible states until you observe it. So, until you observe her, Isabella will be both simultaneously dead and not dead.

**Invader Snik:** The original Slender actually lags really badly on my computer (I know. Pathetic, right?), and it freaks me out too badly to play anyways. And I can't wait for the next chapter, either!

**AuthorD:** Yes. Because I definitely have enough planning skills to decide ahead of time what his plan is...

**Sleeping Kangaroo: **Well, I try my best!

**Cute as a button22:** I can't say anything about Isabella herself, but I can promise Phinbella!

**14AmyChan: **He'd probably follow her just about anywhere!

**awesomejosh8596: **That's exactly the reaction I'm looking for.

**TheCartoonFanatic01:** /innocent face/ The Organization? What Organization?


	7. Chapter 6: The First Discoveries

I know, it's been a really long time since I updated. I've been a little (okay, a lot) distracted. I swear, I'm going to try to do better!

**Phineas**

The agents came back downstairs with Gretchen, she being the last person to be interviewed.

"Alright, we're done here," the first agent said. "Thank you for your cooperation. Don't hesitate to contact us if anything else comes up."

"Oh, could we have another one of your business cards?" Phineas asked. "The first one you gave us seems to have gotten lost."

The second agent pulled one of said cards out of his pocket and handed it to Phineas.

"Well, we'd better be going," he said. "Thank you again."

And with that, they strode out the front door.

A moment of silence followed. Baljeet broke it with the declaration "Alright, something is going on here."

"Gee, really?" Buford asked sarcastically. "Isabella goes missing in the dead of night, a pair of secret agents come and ask us a series of strange questions, and now you realize something's going on?"

"Yes, really," Baljeet replied, ignoring Buford's sarcastic tone. "There is something those two were up to that they are not saying. And I think they know something about Isabella's disappearance."

Ferb nodded at that, and a murmur of assent went around the group.

"Baljeet's right," Phineas said. "I've never heard of the 'Bureau of Special Investigations,' and it seemed like they knew something they weren't telling us."

"But why would they be keeping something from us?" Buford asked. "Is what happened to Isabella, like, a government secret or something?"

Phineas and Ferb shared a meaningful glance.

"It's a possibility..." Phineas said. Buford rolled his eyes.

"Please don't tell me you're actually taking my suggestion seriously," Buford said. Phineas and Ferb both ignored him.

"Perhaps we should find out a bit more about this group before making any assumptions," Ferb said.

"Yes," Phineas said. "Yes, we should."

**Quite a bit later**

Phineas and Ferb's bedroom was abuzz with the sound of clicking keyboard. Most of the kids had ran home to grab their computers, and by now, all of them besides Buford were engaged in internet research. Buford still thought everyone else was making too big a deal out of the agents.

Right now, he was just wandering the room, making fun of everyone on the computer. Right now, he popped a Mountain Dew and leaned over Phineas' shoulder.

"You find anything yet?" he asked. "Well, anything besides 9/11 Truthers and those people who think vaccines cause autism."

Phineas gave a sigh and let his head slump over the keyboard.

"Not yet," he said despondently, ignoring Buford's sarcasm. "I've found a few online rumors about that Bureau the two agents said they were from, but none of them are very specific. I'm not even sure just what its purpose is."

"Well, they're the Bureau of Special Investigations, right? So, they obviously arrest people who mod the Fallout games!"

Phineas shot Buford a quizzical look.

"Do you honestly think anyone reading this will get that reference?" he asked. "And since when are you versed in video game lore?"

"You don't know everything about me."

Phineas sighed and sank back into his seat. Buford rolled his eyes and walked off, sipping his Mountain Dew.

As Buford walked off, Ferb walked into the space he'd vacated.

"Oh, hey, Ferb," Phineas said. "I haven't made any progress on what happened to Isabella, if that's what you're wondering."

"Actually, I was wondering if you're going to take a break anytime soon," Ferb replied. "Everyone else has been taking breaks."

"What are you talking about? This is important, and I haven't been at it that lo-"

Ferb pointed at the digital clock at the bottom of the computer screen. The time read ten twenty-three.

"... Oh," Phineas said. "I guess I have been on here a while."

Ferb held out a soda. After a pause, Phineas took it and got up from the computer.

"I'll be back on in fifteen minutes," he said.

Ferb rolled his eyes and slid back into the seat Phineas had vacated.

With a sigh, Phineas popped open his soda and started walking downstairs. Everyone else was still in his and Ferb's room, so he was alone in the house.

When he got downstairs, he sat down at the table and took a long drink from his soda. He felt a little guilty thinking it, but it was nice to sit down and take a load off.

He was still a little bit on shock about everything. Not only had one of his best friends gone missing, but a pair of agents from some sort of government agents had come around asking questions about it. And the way she'd been acting before she disappeared had been... Strange, to say the least. Out of the blue, she'd come to him one day and told him about hallucinations and amnesia, then ran off back home and showed up the next day like nothing had happened.

Something strange was going on, no doubt, but he couldn't make any sense of it.

He gave a dry, sarcastic chuckle and took another drink. This was all too strange for their quiet, suburban lifestyle- well, barring the skyscrapers to the moon and sorbet machines that turned people into flies. It almost seemed like something out of an urban legend.

A frown crossed his face. Come to think of it, this really did sound like an urban legend. This kind of story seemed like something you would read in a poorly-worded chain letter, along with stories about mirror ghosts and sewer murders

Wait... He remembered hearing about something like this. Some urban legend... What was it called?

There was something thin, he remembered. He strained his memory, trying to remember.

The thin... The thin something. No, not thin. The slender...

And then the lights went out.

He looked up from his soda.

"Crap," he swore. "The power has to go out NOW?"

He got up from the table and started rooting through the kitchen. He remembered they sometimes kept a flashlight in there.

But apparently, now was not one of those times.

Maybe in the garage...

He carefully made his way over, taking care not to trip on anything on the way.

The first place he checked was Lawrence's toolbench. He scrabbled around on the benchtop for a moment, then decided that there didn't seem to be any flashlights.

Well, the car was still in the garage. Maybe they kept one in the glove box.

He opened the passenger door and started rooting around. After a few seconds of searching, his hand closed around one of those dinky survival flashlights.

Then a loud grinding noise came from behind him. He turned to see the garage door sliding up behind him.

An expression of confusion crossed his features. He was sure he hadn't hit the garage door opener; come to think of it, he didn't think they even had a garage door opener in the car.

He walked outside and took a look around with the flashlight. Unsurprisingly, however, the light barely shone three feet in front of him. Had there been some... Garage door-opening maniac, he probably wouldn't have been able to see him.

Putting whatever had happened aside for the moment, he decided to head back in. He turned and started to walk back inside.

Then he heard a loud "thud," a distant, booming noise that seemed to take forever to fade. He turned back and looked around the empty street. It was as dark as before.

He shrugged and started back towards the door. Somebody was probably just playing a boombox with the volume all the way up.

The noise came again, but louder. It sounded like it was a little closer now. Still thinking it was just some idiot playing their music too loud, he turned back and took another look around. Everything seemed to be the same as before, with the strange exception of one of the streetlights. The last time he'd looked, they'd been as dark as the houses around them. Now, a single light at the far end was on.

He squinted. It looked like there was someone standing under it, but he couldn't make out any of their feature. Even so, there was something vaguely ominous about them. Just looking at them sent an edge of fear up his spine.

For a moment, he considered calling out to them, but then thought the better of it. For some reason, their presence made him more eager than before to get back inside. He turned and started back towards the door, walking a little quicker now.

The "thud" came again. It sounded closer now. He turned again, fear creeping into him

The figure was now almost halfway down the street. Now he could make out that they were wearing some sort of suit, like the agents who'd questioned them earlier that day.

"He-hello?" he stammered out. They didn't respond. He choked down a lump in his throat and continued "I thought we'd answered all your questions. Can't you, like, come back in the morning?"

The figure remained silent.

"Well... Fine, then!" Phineas said, growing more fearful by the moment. "Just... Just leave us alone!"

He turned back and started running back to the door. The thudding noise came again, but rhythmical, like the slowed-down beating of a heart. This time, he didn't try to see what it was; he just kept running. He had not conscious reason for it, but whoever that figure was, they terrified him.

A gasp of relief left his lungs when he reached the door. He scrabbled for the handle and tried to twist it open.

It didn't budge.

Refusing to believe it, he tried the handle again. It stayed as stuck as before. The thudding noise stopped

He slowly turned, hoping that the figure would be gone for a reason he couldn't place.

They were.

He slumped against the door, his rapid breathing beginning to slow. His fear slowly began to dissipate, and his expression grew more relaxed. The flashlight fell out of his hand and clattered against the concrete floor.

After a few minutes, he managed to push himself up. He picked up the flashlight and clicked it on.

Nothing happened.

He muttered something to himself and threw the flashlight to the side. Something must have gotten knocked loose. He could probably find his way to the front door in the dark.

A cursory glance to the right of the garage and back towards the house revealed that the front door was just where he remembered. He started back towards it.

Unlike the door in the garage, the front door didn't seem to have mysteriously locked itself. The knob twisted when he pulled it and the door opened when he pushed it.

Then he heard it again. The door lay open before him; he could have just walked through and away from whatever was outside.

But he didn't. Something, be it curiosity, fear, or some other force, compelled him to stop and look back.

For the briefest moment, the light above the front door came on, and he saw it. He saw its height, towering feet above him. He saw its hideous mockery of a formal suit, fitting over it like skin. He saw those innumerable appendages, those tentacles, writhing out from its back.

But most of all, he saw its face. He saw the blank features it had in place of lips, a nose, and eyes. He saw the face of terror, of a being that would never, ever leave and never, ever stop. It would never hear his pleas for mercy, and it would never show pity or remorse.

He fell into the doorway. A scream tried to leave his throat and caught. His consciousness slowly slipped away, and he collapsed on the floor in a dead faint.

* * *

Thanks to everyone who reviewed:

**thedoraemons7**

**EDD17SP: **Of course, if he's doing anything related to Slender Man, he'd better watch out for himself...

**fan-like-irving:** I'll certainly try!

**AuthorD**

**TheCartoonFanatic01: **I'm actually still considering whether or not to add other beings besides the Slender Man. I'd like to adopt elements of the mythology of the Big Three, but I'm afraid of coming off as plagiarizing.

**gamelover41592**

**14AmyChan: **I've actually got some plans for Perry's investigations for future chapters. Stay tuned!

**Leira D. Halloway**

**Sleeping Kangaroo:** STOP BEING SO OBSESSED WITH GRAMMAR, CUZ

**Auxio Ferlan**

**(sorry I couldn't get your name in, my computer's being weird).77:** Please don't kill yourself waiting for me to update...


	8. Chapter 7: Isabella's Problems

**Isabella**

**Two months ago**

Isabella lay slumped over her computer, barely managing to stave off sleep. A yawn forced its way out of her throat before she shook herself awake and tried to restore her concentration. She had been up for four hours so far, trying to find any scrap of information about her present condition. So far, her search had yielded absolutely nothing.

She yawned again and typed in another search. After a few seconds, the results came up, and she scrolled through the first page. Unsurprisingly, nothing she saw seemed remotely relevant. She sighed and laid her head on her desk, trying to think of some line of inquiry she hadn't tried yet.

As she let her mind wander, a drop of blood appeared on the desk. She looked down at it, a little confused. Then another one appeared, and she realized that they were coming out of her nose.

"For the love of..." she swore. She pinched off the bridge of her nose and started to scrabble around for some tissues; she was pretty sure she had a box behind her computer.

A frown crossed her expression as the tissues failed to reveal themselves. She could've sworn she remembered putting them there. She leaned over and looked under her desk, making sure to keep pressure on the bridge of her nose.

Nothing.

She gave a growl of frustration and craned her neck to look over the rest of her room. It was a mess, with dirty clothes and books scattered all around, but she could see the tissues on the foot of her bed.

That was strange. She remembered putting those tissues behind her computer when she had a cold not two days ago.

She put it from her mind and got up to grab the tissues. As she picked up the box, the lamp standing above her bed flickered and went out.

On edge and perhaps a bit more fearful than logic might have dictated, she jumped and dropped the box of tissues.

When, about a half-second later, she realized all that had happened was a light going out, she relaxed a little bit and set about unscrewing the bulb. It was hot, and she almost dropped it before shifting her grip to the metal bit at the end.

Now she needed a replacement bulb. They kept some in the closet, if she remembered correctly.

She dropped the burnt-out bulb in the garbage can and stuck her head into the hallway. It was dark outside, but the hall light was on and she didn't see anything too menacing in the hallway.

She put out her head a bit further and craned it to the sides, trying to make sure that she was alone. Normally, she would have felt sheepish about such precautions, but with all that was going on, she felt it was justified.

After a moment, she decided that there wasn't anyone (or anything) outside her room and nervously stepped outside. Nothing revealed itself.

She took a deep breath. The closet was just a few steps down the hall; she told herself nothing could possibly happen to her in the seconds it would take to walk down there.

But try as she might, she couldn't make herself believe it.

After taking a tentative step into the hall, she ran towards the closet, yanked open the door and pulled herself forwards, almost into the closet. Her breathing was fast and heavy. She looked quickly from side to side, not quite sure what she was looking for, but glad when she didn't see it.

It took her breathing a moment to stabilize, before she started looking around the closet for the light bulbs. She thought she remembered them being on the top shelf...

Her hand passed over a cold surface. She stopped, then moved her hand back and grabbed.

She pulled the object out and breathed a sigh of relief: it was a package of light bulbs. She carefully pulled one out of the packaging and looked back into the hallway.

The light in the living room was flickering. She gulped nervously and hightailed it back to her room.

The moment she was back in her room, she slammed the door shut behind her and locked it. She screwed the fresh light bulb into her lamp, and it turned on just as she was finishing. She took a step back to admire her handiwork.

Then the big light in the ceiling went out.

Her heartbeat seemed to double in the next second. She forced down her rising terror and opened the door a crack. The light in the living room had gone out.

Now her breathing started to get faster, and she closed the door again. Going back out to the closet was out of the question now. For a moment, she considered swapping out the fresh bulb from her lamp into the ceiling light, and then she realized that to do that, she would have to put her room into darkness for a few seconds, and that was definitely out of the question.

Of course, it was a bit past midnight. Maybe it was time for bed anyway.

She shook her head at herself. No. She had to find out what was happening to her.

A yawn forced its way out of her throat. Regardless of how tired I am, she appended to herself.

She slipped into the chair and went over the possibilities in her mind. The most prominent of her symptoms were her memory blackouts, the constant feeling that she was being watched, and the visions of that tall, faceless man in a suit. The only two possible explanations she had come up with were that she was suffering from some sort of mental condition, or that someone was stalking her. Until now, most of her research had been oriented to the first possibility, since she didn't see how someone could be causing the memory blackouts by themself. But since she hadn't come up with anything in her research so far, she wondered if it might be time to give the first explanation a shot.

After a moment's thought, she typed in "faceless stalker amnesia" and hit "enter."

She scrolled down the first page of results. Nothing but rules for a monster in some roleplaying game. She clicked to the next page.

At first glance, there wasn't anything of note. Then her eye caught on something; it looked like a gameplay video for something called "Slender The Arrival." The little bit of descriptive text below read "Slender The Arrival #4 Stop Stalking me Slenderman! ... with Slender Man's faceless head, the one for..."

She had absolutely no idea what the person who wrote this description was talking about, but it was the best lead she'd found yet. She typed the words "Slender Man" into the search engine, hit "enter," and clicked on the first entry.

The first part of the page read "About." She read through the section and her jaw began to drop. Amnesia... A tall man in a suit and without a face... It all fit. Everything.

A smile crossed her face for the first time in days. She felt empowered; like she finally had the ability to control what was going on.

Then the lights went out.

Things went downhill quickly from there.

* * *

And I leave you on that pleasant note! Don't worry, the kids'll get a break next chapter... For now.

Thanks to everyone who reviewed:

**TheCartoonFanatic01: **Scarier than _this _one?

**Tokka who invent BeastlyRavens:** Yeah, this chapter kind of went the same way. It gets less cliched (I think) next chapter, I promise!

**Guest: **XD Yes. Yes, he does.

**Leira D. Holloway:** Until the end of time...

**fan-like-irving**

**AuthorD: **You'll just have to wait to find out!

**14AmyChan**

**gamelover41592: **Well, I think we all knew he would, eventually._  
_

** .77**

**thedoraemons7:** Yup! That's it! End of the book!

**ayahsad167: **Thank you!

**Sleeping Kangaroo: **... You done?


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